Embodiments of the present invention relate to a semiconductor device and a method for fabricating the same, and more particularly to a semiconductor device having passing gates and a method for fabricating the same.
With the increasing development of semiconductor fabrication technology, semiconductor devices can be fabricated to be smaller in size and highly integrated. Specifically, as semiconductor devices are rapidly developing to implement higher levels of integration, a preferred cell layout is rapidly changing from an 8F2 structure to a 6F2 structure.
As the degree of integration of the semiconductor device increases, the distance between a gate (word line) coupled to a cell transistor and a bit line coupled to the cell transistor is gradually reduced. As a result, the capacitance between the bit line and the gate may increase such that the operational reliability of the semiconductor device is likely to deteriorate. In order to improve the operational reliability of smaller and highly integrated semiconductor devices, a buried gate structure has been proposed in which a gate is buried within a semiconductor substrate. For example, the conventional buried gate structure described above can be incorporated within a semiconductor device having a 6F2layout, and can include a metal film formed as a gate electrode to reduce the degree of gate-electrode resistance as a compensating modification.
However, the conventional buried gate structure has an overlap region in which a junction overlaps with a gate, resulting in a Gate Induced Drain Leakage (GIDL) caused by a leakage current from the overlap region. If a gate of a cell array of the semiconductor device is formed as a line type, a gate region (defined as a region incorporating one or more “passing gates”) is buried in a device isolation film defining an active region, and this film-isolated gate region may be formed adjacently to the active region of such a semiconductor device. The passing gates may facilitate the occurrence of GIDL. The GIDL discharges the stored charges in the cell array, and deteriorates retention characteristics (i.e., refresh characteristics) of the semiconductor device.